Microbial response to environmental gradients in a ceramic‐based diffusion system

Abstract

A solid, porous matrix was used to establish steady-state concentration profiles upon which microbial responses to concentration gradients of nutrients or antimicrobial agents could be quantified. This technique relies on the development of spatially defined concentration gradients across a ceramic plate resulting from the diffusion of solutes through the porous ceramic matrix. A two-dimensional, finite-element numerical transport model was used to predict the establishment of concentration profiles, after which concentration profiles of conservative tracers were quantified fluorometrically and chemically at the solid-liquid interface to verify the simulated profiles. Microbial growth responses to nutrient, hypochloride, and antimicrobial concentration gradients were then quantified using epifluorescent or scanning confocal laser microscopy. The observed microbial response verified the establishment and maintenance of stable concentration gradients along the solid-liquid interface. These results indicate the ceramic diffusion system has potential for the isolation of heterogeneous microbial communities as well as for testing the efficacy of antimicrobial agents. In addition, the durability of the solid matrix allowed long-term investigations, making this approach preferable to conventional gel-stabilized systems that are impeded by erosion as well as expansion or shrinkage of the gel.

Biofilm form and function: carbon availability affects biofilm architecture, metabolic activity and planktonic cell yield

“…strain CT07, was used as the test organism for all of the experimentation (Bester et al. 2005; Wolfaardt et al. 2008).…”

“…An environmental isolate, designated as Pseudomonas sp. strain CT07, was used as the test organism for all of the experimentation (Bester et al 2005;Wolfaardt et al 2008). A gene sequence encoding for the constitutive expression of the green fluorescent protein (GFP) was inserted into the chromosome, and cultivation was carried out in modified AB defined media with 1 mmol l )1 Na-CitrateAE2H 2 O as the sole carbon source, as described previously (Bester et al 2009).…”

The Porous Surface Model, a Novel Experimental System for Online Quantitative Observation of Microbial Processes under Unsaturated Conditions

“…The ceramic plate, which is 7.1 mm thick and 41.3 mm in diameter, was chosen because its pores are small enough to exclude bacterial growth inside the plate (specified maximum pore radius, Ͻ1.5 m; 1-bar bubbling pressure plate; Soilmoisture, Santa Barbara, CA). This type of plate has been recently used to expose bacteria to chemical gradients in saturated conditions (30). Prior to use, the ceramic plates were grounded with a 25-m diamond abrasive to minimize surface irregularities.…”

A microfluidic method and custom model for continuous, non-intrusive biofilm viscosity measurements under different nutrient conditions

“…21 Biofilm-forming bacteria were Pseudomonas sp. CT07, which are considered equivalent to Pseudomonas ßuorescens CT07, 58 were cultured at 30 ( C) for 3 days in an LB nutrient Petri dish via streaking. The bacteria were scraped from the surface and suspended in 3 (ml) of the nutrient medium.…”